We have in the past concentrated our scientific efforts on two fronts, namely: l) the development of new and improved neuroanatomical techniqes, and 2) the application of these techniques to the study of primary and higher order olfactory connexions. The current grant period has been a transition period, in the sense that the methodology previously employed in this research has been supplemented, and partly replaced by more sensitive experimental methods, some of which have been developed in our laboratory. We are currently concentrating a large part of our effort to develop a solid HRP-EM method. In this application research support is requested for continuation of our methodological studies, and for experimental neuroanatomical investigations aimed at improving our knowledge of the organization of the basal forebrain in mammals. To accomplish this we intend to study three mutually interrelated subjects: l) the internal organization of the afferent and efferent connexions of the olfactory cortex; 2) the pathways by which the olfactory bulb is related to the rest of the forebrain in general, and to diencephalon in particular, and 3) the ventral strio-pallidal system. The experimental analysis will be aided by a combination of various light - and electron microscopic tracing techniques, including the Golgi method, degeneration methods, the autoradiographic technique and different horseradish peroxidase methods.